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June 3, 2026
SMTP (Simple Mail Transfer Protocol) is crucial for sending out emails from the CRM. Integrating your SMTP provider with the CRM allows for seamless email communication with your contacts. However, users might encounter errors related to sender email configuration. Understanding these errors and knowing how to address them is key to effective email communication.
This section will guide you through the process of troubleshooting your sender email address to ensure that it is correctly set up.
Even after ensuring the sender email is correctly configured and verified, you might still face issues with sending emails. Here are steps to troubleshoot further:
Below are some frequently encountered SMTP error codes, their meanings, and recommended solutions:
400 Errors (Bad Requests):
from/to/message parameter is missing: Ensure the sender’s and receiver’s email addresses and the email body are included in the email.Need at least one of 'text' or 'html' parameters specified: Include at least one version of the email, either in plain text or HTML.Too many recipients; max is 1000: Limit the number of recipients to 1000 or fewer.401 Forbidden: The user lacks the necessary permissions. Verify user permissions for the request.
404 Domain not found: Use a valid, existing domain.
429 Request limit exceeded: Wait until the specified time before trying to send the request again.
500 Internal Server Error: Try the request again later or contact the server administrator.
421, “4.3.0” Temporary System Problem: Retry sending the message later.
450, “4.2.1” The user you are trying to contact is receiving mail too quickly: Resend your message at a later time.
451, “4.3.0” The mail server temporarily rejected the message: Retry sending the message later.
550, “5.1.1” The email account that you tried to reach does not exist: Check the recipient’s email address for typos.
550, “5.4.5” Daily sending quota exceeded: Limit the number of emails you send each day or upgrade your Google Workspace edition.
403 – You are not authorized to send from that email address: Verify the Sender Identity configuration and ensure that the “from” address is correctly set.
421 – Message from (X.X.X.X) temporarily deferred: Reduce the frequency or volume of messages being sent to the recipient domain.
450 – too frequent connects from X.X.X.X, please try again later: Wait and allow the recipient’s mailbox to become available again.
451 – Authentication failed: Maximum credits exceeded: Contact Sendgrid support to resolve the credit limit issue.
452 – Too many recipients received this hour (throttled): Reduce the number of recipients in the message or split the message into smaller batches.
0x800CCC00: Recheck your email and password details. If the problem persists, restart your mail server or contact your ISP for support.
0x800CCC01: Verify that all necessary intermediate certificates are installed. If the certificate is self-signed, ensure that it is installed on both client and server machines.
0x800CCC05: Check your internet connection. If it is stable, there might be server issues. Contact your ISP for assistance.
0x800CCC10: Double-check the email address for any errors or missing information.
0x800CCC11: Check that all the addresses in your list are formatted correctly and remove any that are not.
By understanding these potential issues and following the troubleshooting steps outlined, you can resolve most problems swiftly, ensuring that your emails are delivered successfully.
What if I still receive an error after verifying my sender email?
Can I use a different email for manual emails and automated emails?
How do I prevent SMTP errors?
Can I resend emails after receiving an SMTP error?